If you really have EE degree, you should know that it is mostly a case when you use bipolar transistors. FETs have very different laws, that is why they are used in designs by Nelson Pass and others. Moreover if several transistors are made on the same die, you can use circuits that change transfer function to something like hyperbolic sine, which is almost linear within relatively wide range of values. You can't use similar circuits with tube since there is no two tubes close enough for them to work.

Yes, I really have EE, and I really did my diploma in Tomsk Institute of Semiconductor Devices, and I really believed that approximation of linear function is all that is needed for best sound reproduction, and I really designed several fully complementary, very fast and extremely low distortions (measured!) solid state amplifiers, but that stubborn Tesla Mono-130 tube amp that we had in our laboratory anyway sounded better. It measured worse, but sound was CLEANER! It was BAD, BAD, BAD amp!!!

It took me next 30 years to understand that I was wrong assuming that audible distortions corellate with measured distortions... They do, but not directly. That's why I wrote in my previous post abot SMOOTHNESS of transfer function vs LINEARITY. This is the key. Perception hears as distortion everything that slightly deviates from alterations of sound heard in nature. But if sounds are distorted wildly like reflected from some non-linear wooden surface, or transferred by non-linearly compressed air, they sound clean.
If ou deliberately add 2'nd order distortion you don't improve sound. But if you amplify the signal sacrificing linearity for 2'nd order (and higher orders with higher loudness!) distortions but don't add what people add struggling for linearity, you PRESERVE the sound.
Do you hear me now?

For me the role of amplifier is to transfer signal without changing it in any other way other than volume. Otherwise it will become musical instrument by itself. But I want to listen EXACTLY to what authors (musicians, producers, engineers) intended. That is why any distortion has to be at level low enough not to be heard. It is not possible to achieve with speakers, but any electronic components in playback chain have to be transparent.

previous post about SMOOTHNESS of transfer function vs LINEARITY. This is the key. Perception hears as distortion everything that slightly deviates from alterations of sound heard in nature. But if sounds are distorted wildly like reflected from some non-linear wooden surface, or transferred by non-linearly compressed air, they sound clean.

This is a very important point sadly too often overlooked. Another example is our ability to hear the materials that the room around is made from. A wooden wall sounds very different from a sheet-rock wall, eyes closed (or from a recording).
How can this be? Because we're made to rapidly and automatically ignore *most* sounds, to allow us to react quickly to the tiger behind and above. We *hear* what doesn't belong.

This is a very important point sadly too often overlooked. Another example is our ability to hear the materials that the room around is made from. A wooden wall sounds very different from a sheet-rock wall, eyes closed (or from a recording).
How can this be? Because we're made to rapidly and automatically ignore *most* sounds, to allow us to react quickly to the tiger behind and above. We *hear* what doesn't belong.

Thanks,
Chris

Yes, that is why room treatment is not less important than choice of electronics and speakers.

For me the role of amplifier is to transfer signal without changing it in any other way other than volume. Otherwise it will become musical instrument by itself. But I want to listen EXACTLY to what authors (musicians, producers, engineers) intended. That is why any distortion has to be at level low enough not to be heard. It is not possible to achieve with speakers, but any electronic components in playback chain have to be transparent.

I agree with you that they have to be trasparent Transparent in terms of PERCEPTION. For example, if window glass absorbs UV and above, IR and below, is it transparent? According to measurements it is dirty. But according to human vision it is absolutely transparent. The same with sounds. Now, make it transparent from 1 Hz to the Heavenly frequency, will it be more transparent for vision? Not necessary. Means to increase such transparency can add something that eyes will see as a dirt, as if you see a picture in a frame, instead of a nature through the window. The same with music: either you hear band in your room, or you hear "Nice Sounding Speakers with Linear Amplifier".

I prefer to hear sounds. And enjoy when people say, "I want to buy a house near the creek, I like how frogs are singing on your backyard!"

And it is great reward, when I jump and turn around being scared by running water, then realize that it is a waterfall record from cheap dirty digital CD

Hi DualTriode
Thanks for your feedback and let me say that I must play with the cheaper end of the spectrum, I'm just a TV repairman.
I love the SRPP topology, but the circuit does not have anything extraordinary, I think it can be improved, as I said before the output impedance is too high to drive a power amp, perhaps adding a bypass cap in the bottom cathode resistor can help with.
A long time ago I made calculations with the same circuit and an ECC99, 2K2 resistors and a 470uF bypass cap, maybe I will do a sim.
Best regards
Johann

As explained in post #28 and #36 I consider demonstrated that the electron cloud/space charge affects the linearity of the triode.
Moreover, the curves speak for themselves!!!

Working with triodes, most of us use the information provided by the manufacturer data sheet and work below the dissipation limit curve, which in most cases is in the linear region, as I said in post #36 and #38.

I still have not finished my thesis, you can tell me I'm just a TV repairman if you want, but your PhD degree gives you no right to insult me that way.

Fortunately I am not your student, and I suggest you study a little bit more physics, lest they repent in your university.

I know I found it interesting. I studied physics in some depth, but it's always fun to go back and read about something again.

I notice that this link refers to the fact that the space charge changes the electric field in a 'diode' so that it is no longer linear. Maybe this is what you were thinking of before. Anyhow, what ever the details, it's a fascinating topic.

Your high voltage approach looks interesting and in the true spirit of DIY.

Please don't be put off by the feeling you get from some posts on this forum. Even people who have good English skills are not always aware of how their writing will be received by somebody else. It is the same with email, it is a 'dangerous tool'. And some people just like a good argument

__________________"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.